This invention relates to a key top member for a push button switch structure suitable for use for a data input device, a switch device or the like for mobile communication equipment such as a mobile phone or a car phone, a home telephone, an electronic notebook, a measuring instrument, a vehicle mounted-switch, a remote control, a computer, a personal computer, or the like, and a method for manufacturing the same, and more particularly to a key top member for a push button switch structure which permits a display section such as a symbol, a letter, a pattern or the like printed on a sheet to exhibit enhanced design characteristics and durability and is used for a back-lighted push button switch structure as well.
In general, a push button switch structure for equipment such as mobile communication equipment like a mobile phone, an electronic notebook, a measuring instrument, a remote control or the like is so constructed that a key top member or a cover having key top elements arranged thereon is mounted on a circuit board received in a casing of the equipment, to thereby function as a switch structure for carrying an ON-OFF operation of a circuit of the equipment. Such a push button switch structure typically has a key top member incorporated therein, which is formed of thermoplastic resin into a predetermined configuration by injection molding. Recently, it has been demanded to apply a variety of designs such as a symbol, a pattern and the like to the key top by printing. This is carried out by in-mold techniques or insert molding of applying a variety of designs to a resin sheet by printing, interposedly incorporating the printed resin sheet in a mold for injection molding of a key top and then carrying our drawing of the printed resin sheet concurrently with molding of the key top by means of a pressure of resin being injected rather than techniques of directly subjecting a key top to printing.
Unfortunately, such in-mold forming or injection molding requires an expensive mold for injection molding which is constructed to have a special structure. Also, it causes molding conditions to be severe, leading to a deterioration in productivity and causes a material for the molding to be subjected to a restriction, resulting in an increase in manufacturing cost. For example, the injection molding is carried out while keeping the printed resin sheet placed in the mold, therefore, the printed resin sheet is required to exhibit enhanced heat resistance. Also, the in-mold forming or injection molding requires to provide the mold with an injection gate for each of portions of the printed resin sheet to be subjected to drawing. More specifically, it is required to provide the mold with at least one gate for every configuration of key top elements constituting the key top to be molded. Thus, formation of a plurality of key top elements by molding causes the mold to be expensive and complicated in structure. Also, it is required to inject molten resin for drawing of the printed resin sheet at a high temperature under an increased pressure while adjusting injection conditions for the gates in association with each other. This requires to precisely control temperature conditions, pressure conditions and the like for each of the resin and mold.
Further, in the in-mold forming or injection molding, a portion of the printed resin sheet to be positioned on each of the key top elements is extended by the molten resin, to thereby cause a configuration of a design previously formed on the printed resin to be deformed or shifted, leading to a deterioration in aesthetic properties of the key top finished.
The present invention has been made in view of the foregoing disadvantages of the prior art.
Accordingly, it is an object of the present invention to provide a key top member for a push button switch structure which is capable of being readily manufactured at a reduced cost while having a printed resin sheet interposedly incorporated therein.
It is another object of the present invention to provide a key top member for a push button switch structure which is capable of being inexpensively and readily manufactured without requiring an expensive injection mold.
It is a further object of the present invention to provide a key top member for a push button switch structure which is capable of exhibiting highly enhanced quality.
It is still another object of the present invention to provide a method for manufacturing a key top member for a push button switch structure which is capable of readily providing a key top member attaining the above-described objects.
In accordance with one aspect of the present invention, a key top member for a push button switch structure including at least one key top element is provided. The key top member includes a resin sheet having at least one display section printed thereon and provided with at least one projection having a configuration conforming to an outer configuration of the key top element. The key top member also includes at least one filler member made of photo-setting resin and securely arranged in the projection, to thereby constitute the key top element in cooperation with the projection.
In a preferred embodiment of the present invention, the printed resin sheet acts as an upper resin sheet. The key top member further includes a lower resin sheet securely arranged under the upper resin sheet and filler member through an adhesive. The lower resin sheet may be unfigured or has display sections arranged thereon. The filler member is surrounded by the upper and lower resin sheets while being vertically interposed therebetween.
In a preferred embodiment of the present invention, the lower resin sheet has at least one display section formed thereon in a manner to be different from the display section of the upper resin sheet.
In accordance with this aspect of the present invention, a key top member for a push button switch structure which includes at least one key top element is provided. The key top member includes an upper resin sheet formed to be unfigured and provided with at least one projection having a configuration conforming to an outer configuration of the key top element, at least one filler member made of photo-setting resin and securely arranged in the projection, and a lower resin sheet securely arranged under the upper resin sheet and filler member through an adhesive. The lower resin sheet has at least one display section such as a letter, a symbol, a pattern or the like printed thereon. The filler member is surrounded by the upper and lower resin sheets while being vertically interposed therebetween, to thereby constitute the key top element in cooperation with the projection.
In a preferred embodiment of the present invention, the lower resin sheet is provided thereon with at least one microprojection adapted to press an electrical contact of the push button switch structure.
In accordance with another aspect of the present invention, a method for manufacturing a key top member for a push button switch structure which includes at least one key top element is provided. The method includes the steps of forming a resin sheet having at least one display section printed thereon with at least one projection having a configuration conforming to an outer configuration of the key top element; and securely arranging a filler member made of photo-setting resin in the projection to constitute the key top element in cooperation with the projection.
In a preferred embodiment of the present invention, the resin sheet includes a thermoplastic resin sheet which has a plurality of the display sections previously printed thereon so as to conform to outer configurations of the key top elements. The forming the thermoplastic resin sheet with the projections is carried out by stretching portions of the resin sheet other than portions thereof which correspond to top surfaces of the projections at which the display sections are arranged substantially without stretching the portions corresponding to the top surfaces, to thereby prevent deformation of the display sections printed and misregistration thereof.
In a preferred embodiment of the present invention, the arranging of the filler member includes pouring photo-setting resin in the projection after forming the resin sheet with the projection, and exposing the photo-setting resin to light, to thereby securely cure the photo-setting resin in the projection.
In a preferred embodiment of the present invention, the method further includes the step of arranging an additional resin sheet under the cured photo-setting resin through an adhesive, whereby the filler member is surrounded by the resin sheet having the projection and the additional resin sheet while being vertically interposed therebetween.
In a preferred embodiment of the present invention, the additional resin sheet has at least one display section formed thereon in a manner to be different from the display section of the resin sheet having the projection.
In a preferred embodiment of the present invention, the forming the resin sheet with the projection includes heating the other portions of the resin sheet so as to be softened using a heating die and shaping the resin sheet to be provided with the projection using a forming mold.
In the present invention, the resin for the filler member is filled in the projection of the resin sheet printed or unfigured, to thereby be integrated with the resin sheet due to solidification thereof. Thus, the adhesive may be interposed between the resin sheet and the filler member in view of bonding strength therebetween depending on a material for each of the resin sheet and filler member, forming conditions and the like. The adhesive may be a hot-melt adhesive such as a vinyl chloride resin adhesive, a polyester resin adhesive or the like. Alternatively, it may be a thermosetting adhesive such as an urethane resin adhesive, an epoxy resin adhesive or the like.
Also, in the present invention, the resin sheet having the display section printed thereon or the printed resin sheet may be formed on one surface thereof with an ink receiving layer. The ink receiving layer may be provided with a graphic printing layer including a display section such as a light-permeable letter, pattern or symbol by means of microdots having a plurality of colors including at least cyan, magenta and yellow. The filler member may be arranged on a lower surface of the printed layer. When the display section is formed on the resin sheet by means of a printer, the key top member may be accommodated to a variety of design forming data, to thereby be suitable for not only full-color display at enhanced definition and accuracy but diversified small-quantity production. Also, arrangement of the filler member under the printed display section permits the display section to provide satisfactory brightness and chroma, to thereby exhibit increased visibility. Also, it permits the display section to be readily accommodated to special decoration commonly utilizing metallic decoration, hologram decoration, an actual photograph, computer graphics (CG) or the like, so that the key top member of the present invention may highly appeal to users.
Also, arrangement of the printed display section between the transparent resin sheet and the filler member prevents wear of the printed display section during operation of the key top, to thereby ensure that the display section exhibits enhanced durability and visibility over a long period of time.
Further, the method of the present invention permits a design created by a computer to be applied directly to the printed display section without a making-up step or the like. Also, the printing is carried out on the resin sheet, to thereby inexpensive as compared with printing on a molded article or the like. In addition, it facilitates formation of a layer colored white, silver or the like in an industrial scale. Thus, it permits diversified small-quantity production of the key top to at a low cost.